1c1b0c9570
/dev/tty1..tty6, Alt+F1..F6 or `chvt N`. Each is an independent terminal --
its own screen, cursor, line discipline, foreground process group and
session. Two shells on two terminals are unrelated processes that share a
keyboard and a screen.
What made it possible is a backing store. The console drew straight into the
framebuffer and scrolled by moving pixels, which works exactly as long as
nothing else wants the screen: there was nowhere to put terminal 2 while
terminal 1 was visible, and nothing to repaint terminal 1 from. Each terminal
owns a grid of cells now and the framebuffer shows whichever grid is active,
so vt_switch() is set-index, repaint, return -- nothing is saved on the way
out because the outgoing grid has been current all along.
The rule the layer is built on: a terminal does not know whether it is
visible. Writes land in the grid, the cursor moves, the grid scrolls, all
unconditionally; drawing is one question asked at the bottom of vt.c. Every
alternative spreads "am I on screen" through the escape parser, and then a
terminal switched away from mid-sequence comes back wrong.
Everything that was a single global is per-terminal now: tty_fg_pgrp (deleted),
termios, the input ring, the escape parser, the UTF-8 decoder, and the cursor
-- which also stops being pixels in gfx.c and becomes cells in the terminal.
TIOCSCTTY was `return 0` and now records proc->ctty, which is what /dev/tty
resolves through; /dev/tty was an alias for /dev/console with the same minor,
and they are different questions.
kbd.c names Alt+F1..F6 as KEY_ALT_F1+n, above 0xFF on purpose -- every byte
value is already a character or a UTF-8 continuation, and a chord colliding
with one would be typed into the terminal instead of switching away from it.
What the chord means is decided in console.c, where the terminals are.
VT_ACTIVATE / VT_WAITACTIVE / VT_GETSTATE / VT_OPENQRY, Linux's numbers.
The argument to ACTIVATE is by value, not a pointer -- same shape as TCFLSH.
Two bugs found by screenshotting the result rather than reading the log:
- zsh emits 0x0F to leave alt-charset mode, because that is what the `linux`
terminfo says rmacs is, and the console drew CP437 glyph 0x0F: a sun, in
the prompt, on every line. A terminal never draws a C0 control character.
- SGR 7 was unimplemented, so zsh's partial-line marker rendered as a bare
'#' instead of a reversed block. Reverse video swaps the colours at draw
time, not at store time, so turning it off restores what was underneath.
Verified by screendump: tty1 and tty2 show different screens, and switching
back repaints tty1's earlier content from its grid. schfs-check passes.
docs/architecture/terminals.md, including what it does not do -- no
scrollback, no reflow, no VT_PROCESS mode for a display server to veto a
switch, which Schcom will need before it owns Alt+F7.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VQ7Qx8E1q1M1bbCq8QLHS2
116 lines
5.3 KiB
Shell
116 lines
5.3 KiB
Shell
# /etc/zsh/zshrc — the system-wide interactive zsh configuration for SchOS.
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#
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# Deliberately short. This sets up the things an interactive shell is useless
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# without -- history, completion, and the keys a console sends -- and stops.
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# Anything beyond that belongs in a user's own ~/.zshrc, which is the file zsh
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# reads after this one.
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# ---------------------------------------------------------------------------
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# History
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# ---------------------------------------------------------------------------
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HISTFILE=${HOME:-/root}/.zsh_history
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HISTSIZE=2000
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SAVEHIST=2000
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setopt APPEND_HISTORY INC_APPEND_HISTORY SHARE_HISTORY
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setopt HIST_IGNORE_DUPS HIST_IGNORE_SPACE HIST_REDUCE_BLANKS
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# ---------------------------------------------------------------------------
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# Behaviour
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# ---------------------------------------------------------------------------
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setopt AUTO_CD # `cd /tmp` is implied by typing `/tmp`
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setopt EXTENDED_GLOB
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setopt INTERACTIVE_COMMENTS # a # in an interactive line is a comment
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setopt NO_BEEP # SchOS has no audio, but it would also scroll
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unsetopt FLOW_CONTROL # ^S/^Q are worth more as keys than as flow control
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# ---------------------------------------------------------------------------
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# Keys
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# ---------------------------------------------------------------------------
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# Emacs bindings, because that is what every other line editor on the system
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# does -- mksh's default and the kernel's own canonical-mode editing both.
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bindkey -e
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# Home, End, Delete and the arrows, taken from terminfo rather than written
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# out as escape sequences. The sequences differ between the SchOS console and
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# a serial terminal; the terminal's own description does not.
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typeset -A _sch_keys=(
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"${terminfo[khome]}" beginning-of-line
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"${terminfo[kend]}" end-of-line
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"${terminfo[kdch1]}" delete-char
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"${terminfo[kich1]}" overwrite-mode
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"${terminfo[kcuu1]}" up-line-or-search
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"${terminfo[kcud1]}" down-line-or-search
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"${terminfo[kcub1]}" backward-char
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"${terminfo[kcuf1]}" forward-char
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)
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for _k _w in "${(@kv)_sch_keys}"; do
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[[ -n $_k ]] && bindkey -- "$_k" "$_w"
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done
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unset _sch_keys _k _w
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# A terminal that has just been resized, or that zsh has just taken over, may
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# not have told terminfo yet. This puts the keypad in the mode the escape
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# sequences above were described for, and takes it back out on exit.
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if (( ${+terminfo[smkx]} && ${+terminfo[rmkx]} )); then
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autoload -Uz add-zle-hook-widget 2>/dev/null
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function _sch_zle_init { echoti smkx }
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function _sch_zle_line_finish { echoti rmkx }
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zle -N zle-line-init _sch_zle_init
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zle -N zle-line-finish _sch_zle_line_finish
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fi
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# ---------------------------------------------------------------------------
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# Completion
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# ---------------------------------------------------------------------------
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# Completion is NOT initialised here yet, and the reason is a filesystem
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# measurement rather than anything to do with zsh.
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#
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# A small write to SchFS costs about 58 ms, because every operation is its own
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# transaction group and a commit is two cache flushes and an uberblock write --
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# see the comment at the top of kernel/fs/schfs/kmount.c, which describes the
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# trade-off exactly. Measured on this machine, 200 writes:
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#
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# to one open file on SchFS 11.75 s (58 ms each)
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# open + write + close each 21.39 s (107 ms each)
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# to /dev/null 0.14 s (0.7 ms each)
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#
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# compdump writes the digest with a few thousand separate `print` calls, so
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# compinit -d takes minutes and looks exactly like a hang. compinit itself is
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# fine: with -D, which skips the dump, it finishes in 3.6 seconds.
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#
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# So this waits for deferred commits. When small writes stop costing a disk
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# barrier each, delete this comment and uncomment the three lines below.
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#
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# autoload -Uz compinit
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# compinit -u -d ${HOME:-/root}/.zcompdump
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#
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# Until then, completion is available on demand in a shell you do not mind
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# waiting three seconds for:
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#
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# autoload -Uz compinit && compinit -D -u
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#
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# -u is not optional whenever this is turned back on. Without it compinit runs
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# compaudit, decides the function directories are "insecure" because SchOS has
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# no ownership model to check, and *prompts* for an answer on a shell that is
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# still starting up -- which is a real hang, unlike the one above.
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# These take effect as soon as compinit is turned on above; a zstyle with no
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# completion system to read it is inert, not an error.
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zstyle ':completion:*' menu select
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zstyle ':completion:*' matcher-list 'm:{a-z}={A-Za-z}' # case-insensitive
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zstyle ':completion:*' list-colors ''
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zstyle ':completion:*:descriptions' format '%F{244}%d%f'
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# ---------------------------------------------------------------------------
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# Prompt
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# ---------------------------------------------------------------------------
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# The accent violet from include/theme.h, which is 99 in the 256-colour cube
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# and falls back to magenta on the 8-colour console. The last-status marker is
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# the only thing here that ever turns red -- same rule as the rest of the
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# system: normal states are calm, only failure is loud.
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setopt PROMPT_SUBST
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# The chevron is », not ❯. The console font is CP437 and has a glyph for
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# the first and none for the second, so ❯ renders as '?' -- correctly, since
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# drawing a *different* character would be worse, but it still looks broken.
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PROMPT='%F{magenta}%B%n@schos%b%f %F{cyan}%~%f %(?.%F{green}».%F{red}»)%f '
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RPROMPT=''
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